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Posted by Art on August 6, 2007, 1:32 am
>
>> The pleated filters are much better and are available in the same size as
>> the cheap fiberglass filters. Obviously they have to be changed more
> often
>> but you will see less dust in the house particularly if you go with one
>> of
>> the expensive Filtrete brand filters. If you have a old marginal blower
>> that barely moves enuf air then you should probably go with a filter that
>> does not filter as well as the Filtrete ultra but most newer systems have
>> strong blowers with plenty of capacity. Sometimes they have multispeeds
> and
>> your may or may not be set to run at the optimal speed for a quality
> filter.
>
>
> Just because you have a new furnace with a blower that moves more air
> means
> nothing.
>
> With today's high efficient furnaces you have a few things happening.
>
> #1 high efficient furnaces have thinner heat exchangers to transfer the
> heat
> faster. So the equipment requires more air-flow to maintain a proper
> temperature rise across the heat exchanger. This not only cools the heat
> exchanger, but allows the unit to transfer more heat into the conditioned
> space by cooling down the flu gases. <<<End result - more airflow>>>
>
> #2 the equipment manufactures are concerned about cost per unit. In order
> to
> make their products cheaper, they use less materials/metal. This thinner
> heat exchanger, requires a lower temperature rise than the older models.
> If
> this is compromised, you end up with a cracked heat exchanger that
> requires
> it to be replaced (either with a new heat exchanger or a new furnace).
> <<<End result - more airflow>>>
>
> #3 the blowers are manufactured to operate with-in a range of static
> pressure. Most units today are manufactured with a maximum TESP (total
> external static pressure) of .5" wc. <<<End result - less restrictive HVAC
> components>>>
>
> Now look at the filter you're about to use... many are adding .15-.25" wc
> or
> more to the total. So when you add in the evaporator coil, supply/return
> ducting, supply/return grills, you're above the manufacture's
> specifications!
>
> If you look at the data, you're needing more airflow with less
> restrictions.
> This is why most older duct systems require modifications when installing
> new equipment. If your concern is air filtration, you should look into a
> media type filter. They're less restrictive since they have much more
> media
> material.
>
> BTW, using a highly restrictive filter is the quickest way to kill your
> HVAC
> system!
>
> ***This is a partial list of failures due to high temperature and high
> static pressures!
> ***This doesn't even address the issues that the restrictive filters have
> on
> a cooling system!
>
I've been using Filtrete Ultra filters in the 3 systems in my 10 year old
house for 10 years. Absolutely no problems during that time. According to
Consumer Reports, the Ultra has fair air flow.
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